1. Field of the Invention
The present invention relates to a liquid crystal display device having a wide viewing angle and a high aperture ratio.
2. Discussion of the Related Art
Generally, a liquid crystal display device includes lower and upper substrates facing each other so as to leave a predetermined interval from each other and a liquid crystal layer formed between the lower and upper substrates. The liquid crystal layer is driven by an electric field generated between the lower and upper substrates. The liquid crystal display displays an image by controlling light transmittance through the driven liquid crystal layer.
The currently used liquid crystal layer is a twisted nematic (TN) liquid crystal display device which has a problem with varying the transmittance of light at each gray level in accordance with a corresponding viewing angle. Specifically, the light transmittance is distributed symmetrically in right and left directions but asymmetrically in upper and lower directions, whereby gray inversion is generated.
In order to overcome such a problem, a method is proposed to compensate for the variation of light transmittance in accordance with a corresponding viewing angle by dividing a domain by differentiating a liquid crystal driven in a pixel area.
A liquid crystal display device according to a related art proposed for compensating a viewing angle is explained by referring to the drawings as follows.
FIG. 1A illustrates a layout of a unit pixel of a liquid crystal display device according to a related art.
FIG. 1B illustrates a cross-sectional view along a cutting line I-I′ in FIG. 1A.
Referring to FIG. 1A and FIG. 1B, a liquid crystal display device according to a related art includes first and second substrates 10 and 20, gate and data lines 16 and 18 formed on the first substrate 10 horizontally and vertically so as to define at least one pixel area. A gate insulating layer 12 is formed on the gate line 16, and a passivation layer 14 is formed on the data line 18. A pixel electrode 40 is formed in the pixel area, and an auxiliary electrode 30 is formed on a same layer of the data line 18 so as to be overlapped with a circumference of the pixel electrode 40. A black matrix layer 22 is on the second substrate 20. A color filter layer 24 and a common electrode 50 are formed on the color filter layer 24 so as to have an electric field inducing window 52 inside. A liquid crystal layer (not shown in the drawing) is between the first and second substrates 10 and 20.
Namely, when an electric field is generated between the pixel and common electrodes 40 and 50 formed on the first and second substrates 10 and 20, respectively, a fringe field, represented by the dotted line in FIG. 1B is formed by the electric field formed inside the common electrode 50. Liquid crystals of the liquid crystal layer at both sides of the common electrode 50 centering around the electric field inducing window 52 are aligned differently in accordance with the fringe field. Thus, the liquid crystal display device according to a related art compensates for the varying transmittance of light corresponding to a viewing angle.
Moreover, the auxiliary electrode 30 formed over the circumference of the pixel electrode 40 reinforces the fringe field so as to effectively drive the liquid crystals located around the pixel electrode 40.
Yet, in the liquid crystal display device according to the related art, the auxiliary electrode 30 formed around the pixel electrode 40 is made of metal failing to transmit light as well as leaving a predetermined interval from the data line 18 so as to prevent short circuit with the data line 18. Hence, a width of the pixel electrode 40 is reduced to decrease an aperture ratio, whereby brightness is reduced.
An additional task of increasing luminance of a backlight is required for the application to a device, thereby causing problems such as large power consumption and the like.